1. Field of the Invention
This invention relates to an information signal recording apparatus and more particularly to an apparatus arranged to record with rotary heads an information signal in each of a plurality of areas extending in the longitudinal direction of a tape-shaped recording medium.
2. Description of the Prior Art
Tape recorders recently proposed include a kind arranged to have a magnetic tape wrapped to a given degree of angle about a rotary cylinder which is provided with rotary heads and to record or reproduce digital audio signals by means of the heads individually in or from each of plurality of recording areas longitudinally extending on the magnetic tape.
FIG. 1 of the accompanying drawings shows the tape transport system of the above-stated multi-track digital audio tape recorder of the prior art. FIG. 2 shows the recording tracks formed on a tape by this tape recorder. In FIG. 2, recording areas CH1 to CH6 are arranged to individually have audio signal recorded therein while a head 3 or 4 traces the tape from a point A to a point B, from the point B to a point C, from the point C to a point D, from the point D to a point E, from the point E to a point F and from the point F to a point G respectively as shown in FIG. 1. In each of these areas, the so-called azimuth overlapped writing is performed. However, the recording tracks in each of these areas do not have to be on the same straight line. Further, pilot signals of different frequencies f1, f2, f3 and f4 are recorded for the purpose of tracking control in each of the areas in rotation in the fixed order of f1 - f2 - f3 - f4. However, the pilot signals in each of these areas are not correlated with those of other areas.
Again referring to FIG. 1, in case that signals are arranged to be recorded or reproduced in or from the areas CH1 to CH3 when the tape is allowed to travel at a given speed in the direction of arrow 7 and to be recorded or reproduced in or from other areas CH4 to CH6 when the tape travels in the direction of arrow 9, the inclination of the tracks formed in the areas CH1 to CH3 somewhat differs from that of tracks formed in other areas CH4 to CH6 as shown in FIG. 2. However, the difference between the two directions in the relative speed of the tape and the head presents no problem as the travelling speed of the tape 1 is extremely low compared with the revolving speed of the heads 3 and 4.
FIGS. 3(a) to 3(j) show in a time chart the recording and reproducing operations of the tape recorder which is arranged as described above. FIG. 3(a) shows a phase detection pulse signal (hereinafter referred to as a signal PGa)) which is produced in synchronism with the rotation of the cylinder 2 in a rectangular wave form of 30 Hz alternating a high level and a low level (hereinafter referred to as H and L levels respectively) in a cycle of 1/60 sec. FIG. 3(b) shows a pulse signal PG(b) which is of the polarity opposite to that of the signal PG(a). The signal PG(a) remains at an H level while the head 3 is revolving from the point B to the point G of FIG. 1. The signal PG(b) stays at an H level while the head 4 is revolving also from the point B to the point G.
FIG. 3(c) shows a data reading pulse signal (c) obtained from the signal PG(a). The signal (c) is used for sampling, for every other field, an audio signal produced during a period corresponding to one field (1/60 sec.) portion of a video signal. FIG. 3(d) shows a signal (d) which is produced at an H level representing a signal processing period for adding an error correcting redundant code or the like to the sampled one field portion of the audio signal or data by means of a RAM or the like or for changing the arrangement of the data. FIG. 3(e) shows a signal (e) which is produced at an H level to indicate a data recording period and to show a timing for recording on the tape the data obtained through the above-stated signal processing operation.
Referring to FIGS. 3(a) to 3(j), the temporal flow of signals is as follows: The data sampled during a period between points of time t1 and t3 (during which the position of the head 3 shifts from the point B to the point G) is subjected to the signal processing operation during a period between points of time t3 and t5 (during which the position of the head 3 shifts from the point G to the point A) and is recorded during a period between points of time t5 and t6 (during which the position of the head 3 shifts from the point A to the point B). More specifically, the sampled data is recorded into the area CH1 of FIG. 2 by means of the head 3. Meanwhile, the data which is sampled while the signal PG(b) is at an H level is also subjected to the signal processing operation at a similar timing and is recorded into the area CH1 by the other head 4.
FIG. 3(f) shows a signal PG(f) which is obtained by phase shifting the signal PG(a) to a predetermined extent (or 36 degrees corresponding to one area). In case that an audio signal is to be recorded by using this signal PG(f) and another signal which is of the polarity opposite to that of the signal PG(f), the recorder operates as follows: The data sampled during a period between the points of time t2 and t4 is signal processed according to a signal (g) shown at FIG. 3(g) and is recorded during a period between points of time t6 and t7 according to a signal (h) shown at FIG. 3(h). In other words, the data is recorded in the area CH2 shown in FIG. 2 by the head 3 while the head 3 is tracing the tape from a point B to another point C. The data which is sampled during a period between the points of time t4 and t7 is likewise recorded in the area CH2 by the head 4.
During the period between the points of time t6 and t7 (or between t1 and t2), the signal recorded in the area CH2 is reproduced in the following manner: The head 3 reads data from the tape 1 according to the signal (h) of FIG. 3(h). The data which is thus read is signal processed according to a signal (i) shown at FIG. 3(i) during a period between points of time t7 and t8 (or between t2 and t3) in a manner reverse to the signal processing operation performed during recording. In other words, error correction, etc. are accomplished during this period. A reproduced audio signal which is thus obtained is produced according to a signal (j) shown at FIG. 3(j) during a period between points of time t8 and t9 (or between t3 and t6). Meanwhile, the other head 4 likewise performs a reproducing operation at a phase difference of 180 degrees from the above-stated reproducing operation of the head 3 to give a continuous reproduced audio signal in conjunction with the head 3. For each of other areas CH3 to CH6, the signal PG(a) is phase shifted to a degree of n.times.36.degree. and recording and reproduction are performed according to the phase shifted signal PG(a) in the same manner as the operations mentioned above. These operations can be accomplished irrespective of the travelling direction of the tape.
While the tape recorder of the above-stated kind permits individual use of each area, it has been difficult to simultaneously use the plurality of areas. In other words, since each area is individually used for recording, it is impossible to obtain adequately reproduced signals, RF simultaneously from two of these areas by using one and the same rotary head. In the event of recording which is not performed by so-called azimuth recording, reproduced signals obtained from two tracks partially mix with each other to prevent adequate reproduction. In the case of so-called azimuth overlapped recording, there arises some region, that, gives almost no reproduced signal RF.
Part (a) of FIG. 4 shows the tracing locus of the rotary head obtained during reproduction performed by the conventional tape recorder. In part (a) of FIG. 4, a reference symbol HT denotes the tracing locus of the head. Hatched parts PB indicate parts where the, reproduced signal RF is obtainable. In the case of part (a) of FIG. 4, tracking is allowed to be adequately carried out for the area CH1. Part (b) of FIG. 4 denotes a reproduced signal. As shown, almost no signal is reproduced from the areas CH3 and CH4. This brings about the following problems: In detecting whether or not an audio signal has already been recorded in each of these areas, the area from which no reproduced RF signal is obtained might be mistaken for a non-recorded area. Further, in case that an audio signal (such as a signal BGM) which is related to an audio signal recorded in a first area is recorded in a second area, it is difficult to simultaneously reproduce these signals. In other words, it has been impossible to impart the so-called sound-on-sound function to the tape recorder.